Tetracyanonickelate compounds as sorptive materials and the substitution of their H2O content by D2O

The compounds NiNi(CN)₄·3,5H₂O and Ni(NH₃)₂Ni(CN)₄·H₂O have been studied to examine the possibility of substituting their H₂O or NH₃ content by D₂O. Contact with D₂O was performed after heating the compounds to several temperatures. Depending on the degree of decomposition of the original compounds different ranges of substitution were possible. In such manner the compounds NiNi(CN)₄·3,5D₂O, NiNi(CN)₄·5D₂O, Ni(NH₃)₂Ni(CN)₄·D₂O, and Ni(D₂O)₂Ni(CN)₄·D₂O were prepared and thermally they were less stable than the original ones. The substitution by D₂O is in agreement with the sorptive properties of the original tetracyanonickelate against different organic compounds using GC, since these could substitute the guest component and sometimes also the ligands during their decomposition.     

Determination of bromate in drinking water by zone electrophoresis-isotachophoresis on a column-coupling chip with conductivity detection

The use of capillary zone electrophoresis (CZE) on-line coupled with isotachophoresis (ITP) sample pretreatment (ITP-CZE) on a poly(methylmethacrylate) chip, provided with two separation channels in the column-coupling (CC) arrangement and on-column conductivity detection sensors, to the determination of bromate in drinking water was investigated. Hydrodynamic and electroosmotic flows of the solution in the separation compartment of the chip were suppressed and electrophoresis was a dominant transport process in the ITP-CZE separations. A high sample load capacity, linked with the use of ITP in this combination, made possible loading of the samples by a 9.2 microL sample injection channel of the chip. In addition, bromate was concentrated by a factor of 10(3) or more in the ITP stage of the separation and, therefore, its transfer to the CZE stage characterized negligible injection dispersion. This, along with a favorable electric conductivity of the carrier electrolyte solution, contributed to a 20 nmol/L (2.5 ppb) limit of detection for bromate in the CZE stage. Sample cleanup, integrated into the ITP stage, effectively complemented such a detection sensitivity and bromate could be quantified in drinking water matrices when its concentration was 80 nmol/L (10 ppb) or slightly less while the concentrations of anionic macroconstituent (chloride, sulfate, nitrate) in the loaded sample corresponding to a 2 mmol/L (70 ppm) concentration of chloride were still tolerable. The samples containing macroconstituents at higher concentrations required appropriate dilutions and, consequently, bromate in these samples could be directly determined only at proportionally higher concentrations.     

Study of the binding sites in the biomass of <Emphasis Type="Italic">Aspergillus niger</Emphasis> wild-type strains by FTIR spectroscopy

Fourier transform infrared (FTIR) spectroscopy studies were performed to confirm and to provide information on the identity and binding characteristics of the chemical groups responsible for the binding of elements using Aspergillus niger (A. niger) wild-type strains. Two absorption bands in the 3690–3615 and 2970–2895 cm^?1 regions can characterize stretching vibrations OH and CH groups in fatty acids, respectively, and intensive bands around of 1600 cm^?1 and by 1048 cm^?1 correspond to stretching vibrations of C=O groups of amides (amide I) or stretching vibrations ν(C–N). The FTIR results confirmed that no extra differences between IR spectra of A. niger in raw biomass and in solid rest after extraction with chloroform were observed. The small differences were observed in IR spectra of A. niger in chloroform after extraction.     

The Possibility of TLC-FID Detection in Oligosaccharide Analysis

JPC – Journal of Planar Chromatography – Modern TLC - Thin layer chromatography with flame-ionization detection has been used for analysis of oligosaccharides. We report preliminary...     

DNA-based biosensors with external Nafion and chitosan membranes for the evaluation of the antioxidant activity of beer,coffee, and tea

Novel electrochemical DNA-based biosensors with outer-sphere Nafion and chitosan protective membranes were prepared for the evaluation of antioxidant properties of beverages (beer, coffee, and black tea) against prooxidant hydroxyl radicals. A carbon working electrode of a screen-printed three-electrode assembly was modified using a layer-by-layer deposition technique with low molecular weight double-stranded DNA and a Nafion or chitosan film. The membrane-covered DNA biosensors were initially tested with respect to their voltammetric and impedimetric response after the incubation of the beverage and the medium exchange for the solution of the redox indicator [Fe(CN)₆]^3?/4?. While the Nafion-protected biosensor proved to be suitable for beer and black tea extracts, the chitosan-protected biosensor was successfully used in a coffee extract. Afterwards, the applicability was successfully verified for these biosensors for the detection of a deep degradation of the surface-attached DNA at the incubation in the cleavage agent (hydroxyl radicals generated via Fenton reaction) and for the evaluation of antioxidant properties of coffee and black tea extracts against prooxidant hydroxyl radicals. The investigation of the novel biosensors with a protective membrane represents a significant contribution to the field of electrochemical DNA biosensors utilization.      

Stereoconservative Negishi arylation and alkynylation as an efficient approach to enantiopure 2,2'-diarylated 1,1'-binaphthyls

Negishi arylation and alkynylation of easily synthesized chiral 2,2'-diodo-1,1'-binaphthyl rapidly proceeds in refluxing THF utilizing controlled microwave irradiation, affording enantiopure 2,2'-diarylated 1,1'-binaphthyls in good to excellent yields.     

The endomorphism spectrum of a monounary algebra

The endomorphism spectrum specA of an algebra A is defined as the set of all positive integers, which are equal to the number of elements in an endomorphic image of A, for all endomorphisms of A. In this paper we study finite monounary algebras and their endomorphism spectrum. If a finite set S of positive integers is given, one can look for a monounary algebra A with S = specA. We show that for countably many finite sets S, no such A exists. For some sets S, an appropriate A with spec A = S are described. For n ∈ ? it is easy to find a monounary algebra A with {1, 2, ..., n} = specA. It will be proved that if i ∈ ?, then there exists a monounary algebra A such that specA skips i consecutive (consecutive eleven, consecutive odd, respectively) numbers. Finally, for some types of finite monounary algebras (binary and at least binary trees) A, their spectrum is shown to be complete.     

Removal of selected chlorinated micropollutants by ozonation

Feasibility of ozone oxidation for the elimination of selected dissolved organic micropollutants from water and wastewaters was studied. Five organochlorine pesticides, i.e. hexachlorobutadiene, pentachlorobenzene, hexachlorobenzene, lindane, and heptachlor, were used as organic contaminants of model water. The first four of them are classified as priority hazardous substances. The oxidation treatment process was performed in a jet loop reactor. Ozone was prepared from pure oxygen. Quantification of the organochlorine pesticides in water was achieved by the gas chromatographic method after liquid-liquid extraction. Significant contribution of stripping to the removal of the investigated compounds during the ozonation treatment was also proven by the results. Effective ozonation time with regard to treatment efficiencies was 30 min, which corresponds to the ozone input of 317 mg per liter of active volume of the ozonation reactor. Single power law kinetic models were used to describe experimental data and kinetic parameters were estimated. The best fit of the experimental degradation data of all studied pollutants was obtained by the second order kinetic model. It can be concluded, based on the results obtained, that the applied ozonation process is a promising procedure for the removal of the investigated pesticides from aquatic environment.     

An Improved Method for Determination of Polychlorinated Biphenyls and Polybrominated Diphenyl Ethers in Sediment by Ultrasonic Solvent Extraction Followed by Stir Bar Sorptive Extraction Coupled to TD–GC–MS

An improved simple, fast and miniaturized method for the determination of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in freshwater sediment using ultrasonic solvent extraction followed by stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry (USE-SBSE/TD–GC–MS) is presented. The sediment sample (0.2 g) is extracted with methanol (1:1.2, 2:1.0 mL) in an ultrasonic bath (two 5-min extraction cycles). The combined extracts are made up to 5 mL with water, and from the resulting solution, the analytes are preconcentrated on a stir bar coated with polydimethylsiloxane during 1 h of stirring. The loaded sorptive stir bar is then thermally desorbed and online analysed by GC–MS. For the analytes in river sediment, a linear dynamic range of 0.5–50 ng g^?1 was established and limits of detection in sub nanogram-per-gram level were achieved. Recoveries and repeatability were obtained in the ranges 62.8–91.5 % and 3.6–15.0 %, respectively. The method accuracy was confirmed by the analysis of PCBs and PBDEs in a certified reference material. The main improvement in comparison with similar published methods is in shortening the sample handling time and the method miniaturization.